a subject that is being discussed or studied : the subject on which people's attention is focused—usually singular
a main purpose or interest
a point at which rays of light, heat, or sound meet or from which they move apart or appear to move apart; especially : the point at which an image is formed by a mirror, a lens, etc.
the part of a plant that is often brightly colored, that usually lasts a short time, and from which the seed or fruit develops —sometimes used figuratively.
a small plant that is grown for its beautiful flowers